KR100748498B1 - How to read a file on an embedded system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of reading a file of a program running on an embedded system without a file system. In general, the program source code must be modified to load a file into a memory and read file input functions from the memory. do. However, in the case of an application program interface (API) that needs to receive or return a file pointer (fp) as a parameter, a normal operation of the program may not be performed when modified without considering the file pointer (fp). There was this. Therefore, in the present invention, the field (_base) indicating the start pointer of the file, the field (_cnt) indicating the total size of the file, and the field (_ptr) indicating the next start pointer of the file are designated as addresses in memory. Set to open the file, read and store a block of a certain size (len = size1 * size2) in the data pointed to by the pointer (_ptr), and store the pointer (_ptr) by the size (len). By modifying the source code to read the file in increments and closing the file, porting software with a lot of file reading code to embedded systems without a file system can interfere with the overall software behavior. It has the same effect as reading a file without giving it a chance.

Description

FILE READING METHOD FOR EMBEDDED SYSTEM}

1 is an exemplary view showing a conceptual configuration of an embedded system provided with a file system.

2 is an exemplary view showing a file structure commonly used for a file input / output function.

3 is an exemplary view showing a format of a file converted for applying the present invention.

4 is an exemplary view showing a conceptual configuration of an embedded system without a file system.

The present invention relates to a file reading method of an embedded system, and more particularly, to a file reading method of an embedded system that enables a file pointer to be read by manipulating a file pointer in an embedded system without a file system.

The file system is a part of the overall storage management system, and mainly refers to a system that manages files on the auxiliary storage device, and includes a computer system such as an MS-Dos file system, a UNIX file system, and a network file system. There are several ways.

More specifically, a file system is a method or data structure that the operating system uses to keep files on a partition or disk, and refers to a partition or disk used to store files. Also used to refer to the form of.

The difference in the filesystem that a disk or partition contains is important, as some programs (including those that make a reasonably sufficient filesystem) directly manipulate the raw sectors of a disk or partition.

Most programs run on top of filesystems and do not work on partitions without filesystems (or other types of filesystems).                         

In order for a partition or disk to be used as a filesystem, it must be initialized and a data structure must be created on disk to record file information.

On the other hand, when porting certain software to an embedded system, the software content may include a part that reads a file.

By the way, an embedded system may or may not have a file system (a kind of auxiliary storage device such as a hard disk).

Therefore, as shown in Fig. 1, if there is a file system, even if there is a part that reads the file in the software content, no special processing is required, but if there is no file system, the file is loaded into memory. In general, the program source code must be modified to read file input functions from memory.

However, if there is an API that needs to get or return a file pointer (file pointer, fp) as a parameter in the program, if the modification without considering the file pointer (fp) can not expect the normal operation of the program.

This is because the API does not know when and how to call it in a program. For this reason, the question of how to change the source code that leads a file is very important.

Therefore, the present invention has been created to solve the above-mentioned conventional problems, the file reading method of the embedded system to read the file loaded in the memory using a file pointer in the embedded system (Embedded system) without a file system The purpose is to provide.

In order to achieve the above object, the present invention provides a function caller that calls an API including a file reading content, and by calling this API, the same effect as that of actually reading a file on a file system can be obtained. do.

 In addition, the present invention is characterized in that it does not cause a malfunction to other APIs that use the same file pointer because of the file pointer passed to the API in parameter form.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

According to the present invention, when a file is loaded on a memory in hexadecimal form in an embedded system without a file system, the file pointer is manipulated to read the file in the file system.

FIG. 2 is an exemplary view showing a file structure commonly used for a file input / output function. A case in which a file to be loaded is 'Status_bar.gif' will be described as an example.

As shown in FIG. 3, the memory is stored in hexadecimal form as an unsigned char type, and the total length is stored as a 32-bit long type.

As described above, the format of the file to be loaded into the memory can be easily converted by an engineer working in the same industry by creating a simple conversion program, and thus a detailed description of the format conversion will be omitted.

When the file (Status_bar.gif) is loaded on the memory rather than the file system as described above, each file input / output function recognizes the memory as the file system by slightly modifying the source code related to the file as shown in Table 1 below. This allows operation without overall modification of the program source.

Usage Original function Invention code Open file fp = fopen (status_bar.gif, "r"); fp-> _ ptr = status_bar; fp-> _ cnt = status_bar_size; fp-> _ base = status_bar; File Close fclose (fp); Do not process File read fread (data, size1, size2, fp); if (status_bar_size! = 0) {len = size1 * size2; memcpy (data, fp-> _ ptr, len); fp-> _ ptr + = len; if (len <fp-> _ cnt) count = len; else count = fp-> _ cnt; fp-> _ cnt- = count; } File size status_bar_size;

Here, '_ptr' represents the next starting pointer in the file, '_cnt' represents the total file size, and '_base' represents the starting pointer of the file. Unlike '_ptr', the starting pointer does not change.

For example, suppose you have the following function:

File_read (FILE * fp)

{                     

fread (data, size1, size2, fp);

}

If you apply the general code to read the file loaded in memory instead of 'fread' in the function, the parameter 'fp' has no change, affecting the overall software function.

However, if the source code of the file input / output function is modified using the method according to the present invention, since the manipulation is applied to the file pointer 'fp', the software operates normally and outputs the desired result.

That is, the entire embedded system reads a file from the file system using a file input / output application program interface (API), but as shown in FIG. 4, by modifying the API with the code according to the present invention, the overall system operation is performed. It does the same thing as having a file system without sacrificing this.

As described above, in the file reading method of the embedded system of the present invention, when porting the software having a large number of file reading codes to an embedded system without a file system, the method of reading a file without interrupting the overall software operation is performed. It works.

Claims (2)

When reading an arbitrary file stored in memory in an embedded system without a file system, a field (_base) indicating the start pointer of the file, a field (_cnt) indicating the total size of the file, and Opens the file by setting the field (_ptr) that points to the next starting pointer as an address in memory, and reads and stores a block of a predetermined size (len = size1 * size2) in the data pointed to by the pointer (_ptr). And modifying the source code to read the file by increasing the pointer (_ptr) by the size (len), and closing the file. The file size _cnt at the time of reading the file, wherein the block size len is set to an arbitrary value when the block size len is smaller than the file size _cnt. If the file size (_cnt) is smaller than the block size (len), the file size (_cnt) is set to an arbitrary value (count). And reduce the file size (_cnt) by the set value (count).

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